Rare earth elements (REEs) and other high value strategic materials are elements whose unique properties are essential to the manufacture of high-tech industrial, medical, and military technology. The REE group is considered to include the lanthanide elements: lanthanum, cerium, praseodymium, promethium (does not occur naturally), neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. The elements yttrium and scandium are also included as they have similar chemical properties. Other materials to which aspects of this application is directed include tantalum, titanium, tungsten, niobium, lithium, palladium, vanadium, zirconium, beryllium, thorium and uranium. The above materials are referred to herein as strategic materials for simplicity. Those skilled in the art will appreciate analogous and similar materials to which the present disclosure can be applied as well.
The REEs and the other strategic materials are used in our cell phones, computers, and televisions, as well as in hybrid automobiles, high speed trains, wind turbines, lasers, sonar and fiber optics. They are also important to national security, as they are used in the manufacture of guided missiles, communications satellites, radar, early warning systems, and countless other military and defense items.
Tantalum metal is an example of a high value material that is widely used in its elemental form but found in nature in the form of a salt or oxide compound. Tantalum is used to make steels with desirable properties such as high melting point, high strength, and good ductility. These find use in aircraft and missile manufacture. Tantalum is relatively inert and thus useful in the chemical and nuclear industries. The metal is also highly biocompatible, therefore, tantalum has widespread use for surgical use. For instance, it can be used in sutures and as cranial repair plates. The metal is also used in the electronics industry for capacitors.
Uranium, in its enriched form, is of particular interest as a fuel for nuclear reactors in both commercial and military applications. The overall flow sheet for Uranium includes mining, milling (to produce yellow cake), conversion, and fabrication. Each comprises a number of sub-steps. Following use of the finished product in a nuclear reactor, spent fuel may be reprocessed and/or stabilized and stored. Means for reprocessing spent fuel and management of high level nuclear waste is of substantial consequence.
U.S. Pat. No. 3,429,691 is directed to a method for reducing titanium dioxide powder to elemental titanium. The method combines titanium dioxide powder melted into droplets, and hydrogen plasma, producing liquid titanium and water at the other end of the chamber. The injected hydrogen plasma serves to both heat the titanium dioxide and remove the oxygen from the titanium by reduction. The reaction occurs in a compressing magnetic field in order to prevent the contents from contacting the sides and melting them.
In one example of current practice, Tantalum is produced by metallothermic reduction of one of its salts. At approximately 800° C., solid potassium heptafluorotantalate (K2TaF7) and liquid sodium are added to a halide melt (known as a “diluent”) where they react to produce solid tantalum in the form of powder. The process involves many unit operations prior to the reduction step in order to convert ore to high quality feed. Then, the reduction step relies on a batch process involving very dangerous liquid sodium at temperatures approaching its boiling point (883° C.). The sodium is delivered to the reactor in large vessels (railway tank cars) and stored on site. In this reactor it is difficult both to control particle size and to prevent particle agglomeration, which is critical to the production of high-grade powder for use in capacitors.
The above systems generally require highly reactive liquid sodium and costly potassium heptafluorotantalate double salt feedstock, and lack continuous throughput, and are based on batch operation methods, and further lack the capability to control particle size in the product tantalum powder.
Generally, when the constituents of a mixture or the elements within a compound have an electric charge, one method of separating them relies on accelerating the charged particles and passing them through a magnetic field that is perpendicular to their velocity. This technique of separation separates the particles based on their mass-to-charge ratio.
U.S. Pat. No. 3,722,677 is directed to a device for causing particles to move along curved paths inside a cylindrical chamber using perpendicular electric and magnetic fields, for the purpose of separating the particles. In this invention electrodes can be placed at one or both ends of the confined volume. The positively charged particles will rotate around the central axis and impart this motion to the uncharged particles through collisions. The concentration of heavier particles will be greater at greater radial distances, thus allowing separation.
One way of creating charged particles in a mixture or a chemical compound is by raising the temperature of the material to above that of its gas phase. This transforms it to a state of matter called plasma that is similar to the gas phase except that it has been heated to the degree that some portion of the molecular constituents have lost some of their electrons and are said to be “ionized”. The chemical bonds are broken thermally—the degree of ionization depends on the temperature. A plasma is thus comprised of charged particles—generally positive ions and negative electrons.
U.S. Pat. No. 6,096,220 (“Plasma Mass Filter”), a drawing from which is reproduced in FIG. 1, which is directed to a process and device 10 for filtering low mass particles from high mass particles in a plasma by means of injecting the plasma into a cylindrical chamber having a magnetic field aligned with the axis, and a perpendicular electric field so as to cause a rotational movement of charged particles in the chamber. The magnitude of the magnetic and electric fields are adjusted such that the high mass particles escape radially and collide with the cylindrical wall, while the low mass particles are confined to travel within the walls.
The general function of a filter is quite different from that of a separator. While the former generally requires only that all particles above a certain mass are trapped and all below such a mass pass through—momentum resolution is not a critical design or performance issue. The latter must cleanly separate and collect specific particles that represent the ionic constituents of a particular metal product. Moreover, it is often the case that there is not a large difference in the relative mass of the product particles. For these applications it may be helpful to obtain a measure or parameter related to momentum resolution.
U.S. Pat. No. 6,248,240 is a continuation in part of U.S. Pat. No. 6,096,220 and discusses a non-cylindrical chamber and a plasma source being located midway down the chamber. In addition it provides a method for maintaining a multi-species plasma at a low enough density such that collisions between the particles are relatively infrequent, and introduces one or more collectors positioned to intercept high mass particles.
U.S. Pat. No. 6,235,202 is another continuation in part of U.S. Pat. No. 6,096,220, which discusses injecting vaporized material into the chamber, and then ionizing it inside the chamber to create a plasma.
In some aspects, the present systems and methods improve mineral extraction efficiency, reduce the price of REEs and other high value strategic materials, and reduce the time required to bring a new ore body into production.